Ok, at the moment I run a GTX 460 Hawk that runs about at 915 MHz so I can do some other things. This allows me to be at about 55 Mhash's. If I bought another GTX 460 OC card, and SLI them, would that make any profit at all, or just a waste of money?

edit: also, is it better to mine in smaller pools such as bitcoins.lc or bigger pools such as slush's pool (I currently mine in that one)?